The present invention relates to an optical disk device which reads and replays data recorded upon an optical disk such as a DVD or the like.
Optical disk devices which record data upon recording media are per se generally known and popular. Such an optical disk device irradiates laser light upon the recording surface of the optical disk, and reads the data which is recorded upon this optical disk by detecting the reflected light. During replay, the optical disk device performs various types of servo control. Types of such servo control are rotational speed control of the optical disk (rotational speed control of a spindle motor), control of the condensation upon the recording surface of the optical disk of the laser light irradiated upon this optical disk (focus control), control of the irradiation of the laser light irradiated upon this optical disk upon the center of the track from which data is being read (tracking control), and the like. In such servo control, drive units such as the spindle motor, a thread motor, an actuator which supports an objective lens of a pickup head, and the like are driven. On the other hand, in a stopped mode in which replay of the data which is recorded upon the optical disk is stopped, these drive units are not driven. Due to this, the load upon the power supply which supplies operating power to the drive units is different in a replay mode in which data which is recorded upon the optical disk is being replayed, and in the stopped mode. Thus, if the output of the power supply which supplies operating power to the drive units is the same in the replay mode and in the stopped mode, then the circuit components which are connected to the output side of this power supply will generate heat in the stopped mode.
Furthermore, power supplies which vary their outputs in response to fluctuation of the load are described in Japanese Laid-Open Patent Publication H07-182056, Japanese Laid-Open Patent Publication H08-51772, and Japanese Laid-Open Patent Publication H09-311655.
However, a typical optical disk device is built so as to obtain a first power supply voltage which is used in logic processing and a second power supply voltage which is used for driving the above described drive units from an AC-DC power supply which employs a transformer. The first power supply voltage is taken off from an intermediate point of a coil of a transformer from which the second power supply voltage is taken off. The optical disk device employs a shunt regulator in order to control the second power supply voltage to a predetermined voltage. In concrete terms, a voltage obtained by voltage dividing the first power supply voltage is connected to a detection voltage input terminal of the shunt regulator, and the second power supply voltage is controlled to a predetermined voltage by this shunt regulator.
On the other hand, the load imposed by logic processing is the same in the replay mode and in the stopped mode. The load upon the first power supply voltage is approximately the same in the replay mode and in the stopped mode. With a prior art type optical disk device, there has been no structure for changing over the voltage which is inputted to the detection voltage input terminal of the shunt regulator in the replay mode and in the stopped mode. As a result, it has not been possible to change the second power supply voltage which is used for driving the drive units according to fluctuations of the load in the replay mode and in the stopped mode. Due to this, with a prior art optical disk device, in order to prevent generation of heat by the circuit components which are connected in the output line of this second power supply voltage, high priced circuit components of high rating with respect to generation of heat have been used, so that there has been a problem of high cost.
A feature of the present invention is to provide an optical disk device, with which, along with preventing generation of heat by the circuit components in the stopped mode, also a reduction in cost may be anticipated.